1. Field of the Invention
The present invention relates to an image processing apparatus which receives code information such as PDL data and encodes image data generated based on the code information, and a control method therefor.
2. Description of the Related Art
A general page printer requires a page memory for accumulating a one-page image. For example, a printer capable of printing an A3 full-color image (24 bits per pixel) at a resolution of 400 dpi requires a memory as large as 96 Mbytes, which accounts for a large part of the cost.
One solution to this problem is an image compression algorithm such as a JPEG encoding technique (e.g., Japanese Patent Laid-Open No. 07-066965). This algorithm compresses image data by DCT transformation and quantization, and decompresses the data in real time when printing it out. This can reduce the amount of uncompressed image data to about 1/10 or less, greatly decreasing the memory cost.
To improve the image quality, data must be processed not at a bit precision of 8 bits per pixel but at a higher bit precision of 10 bits per pixel, as shown in FIG. 6.
Compressing image data expressed by 10 bits per pixel, unlike conventional image data, may influence the compression/decompression speed, rendering speed, or data transfer speed because the original data amount is larger than the conventional one.